The present invention generally relates to the field of temperature measuring instruments. Specifically, the present invention relates to the field of measuring air and ocean surface temperature profiles from a ship underway at sea and allows accurate discernment of the temperature difference between the air and ocean surface.
A surface evaporation duct generally exists at the interface of large bodies of water, such as the oceans, and the atmosphere. This duct can cause refraction of electromagnetic radiation propagated through it. Such refraction can seriously impact the effectiveness of radio communications, radars, and radio navigation transmissions because the transmissions may be refracted away from the path of their intended destination. Refraction could also provide false indications of the direction of propagation of transmissions which could result in inaccurate identification of the location of an aircraft or ship.
The refractive properties of the surface evaporation duct are dependent upon the air temperature and moisture profiles immediately adjacent the ocean surface. The ocean surface temperature can significantly affect the refractive properties of the surface evaporation duct. Therefore, the temperature difference between the air and ocean surface is an important factor which must be considered when attempting to predict the overall refractive properties of the surface evaporation duct.
Various types of instruments have been developed which can separately measuring either air or water temperature. U.S. Pat. No. 4,749,254, by Seaver, discloses an optical sensor system for measuring water temperature, index of refraction, and water pressure. The sensors and optical circuitry are contained within a torpedo shaped expendable probe vehicle. The temperature sensor is a selenium prism. The probe vehicle is deployed from a vessel into the ocean to begin a gravity induced free-fall which cause an optical fiber wave guide to unreel within the probe vehicle. The wave guide is operably coupled to a spectrograph recorder positioned on board the vessel. Values of temperature, pressure, and index of refraction are continuously recorded as the probe vehicle descends into the depths of the ocean.
Another type of instrument for measuring a water temperature profile is an expendable bathothermograph probe, such as manufactured by Sippican Ocean Systems, Inc., Marion, MA. This device contains a thermistor located in the nose of the probe. Changes in water temperature are recorded by changes in the resistance of the thermistor as the probe falls through the water. Resistance values are telemetered along two-conductor signal wire to a shipboard data processing system.
U.S. Pat. No. 4,044,611 by Kaname, et al. discloses an expendable oceanography probe for detecting ocean temperature profiles. This device includes a thermistor positioned at the forward end of the probe, an oscillating circuit, and an acoustical disc transducer for radiating a sound signal into the water corresponding to the detected temperature of the water. The resistance of the thermistor is functionally related to the water temperature. The resistance is detected by the oscillating circuit which outputs an electrical pulse signal having a period corresponding to the detected temperature. A piezoelectric ceramic transducer receives the pulse signal and resonates at an ultrasonic frequency corresponding to the water temperature. In the operation of this device, the probe is thrown into the sea from a moving ship and falls vertically through the water. The ultrasonic sound pulse signal which is radiated from the transducer of the probe is received by a receiving transducer installed onboard a ship below the water line.
A problem with all of the above devices is that none of them has a sufficiently low enough time constant to enable it to be deployed in a manner which would enable it to also measure an air temperature profile uninfluenced by thermal contamination of the ship from which it is deployed.
Ocean water temperature has also been measured by detecting the temperature of ocean water passing through the sea water intakes of shipboard power plant cooling systems. However, the temperatures detected by this method are also contaminated by the thermal influence of the ship. Furthermore, they do not accurately detect ocean surface water temperature because the sea water inlets may be at depths of up to 40 feet below the ocean surface.
Air temperature has typically been measured at sea on ships with hand-held thermometers or by remote air temperature sensing instruments typically mounted on a mast of the ship. However, this method is not accurate enough for detecting surface duct evaporation conditions because the detected temperatures are typically contaminated by the thermal influence of the ship.
Therefore, a need exists for a simple device which can measure air and ocean temperatures from a moving ship beyond the thermal influence of the ship so that the difference between the air temperature just above the ocean surface and the ocean surface temperature can be determined.